High-performance rockets with solid-propellant motors may have their flexibility enhanced by providing them with thrust modulation and multiple start-stop capabilities. However, these characteristics are not obtainable with conventional fixed-nozzle designs. It has consequently been suggested that means be provided whereby the nozzle area may be varied during flight in accordance with the particular mode of rocket operation desired. Efforts to achieve results have not heretofore been successful due to an unpredictably uneven erosion of the material of which the nozzle is composed as well as to the uncertainties of combustion chamber dynamics.